System and method for monitoring electrolyte levels in a battery

ABSTRACT

A measuring device is used in conjunction with a programmable controller for monitoring electrolyte levels in the battery. According to one implementation, the measuring device is located in a battery and is configured to detect when the electrolyte level in the battery falls below a particular level. The controller is in electrical communication with the electrolyte detection device. The controller is configured to: (i) receive a signal from the electrolyte level detection device indicating when the electrolyte level in the battery has fallen below the particular level; (ii) introduce a wait-period after the signal is received; and (iii) enable an indicator to indicate that the electrolyte level in the battery should be refilled when the wait-period expires.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims benefit of U.S. ProvisionalApplication Ser. Nos. 60/477,989 and 60/484,855 filed on Jun. 12, 2003and Jul. 3, 2003, respectively. The contents of the aforementionedapplications are fully incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to batteries, and more specifically, tomonitoring electrolyte levels in batteries.

BACKGROUND

Many industrial batteries, for example fork truck batteries, contain anelectrolyte solution used for storing and conducting electrical power.Over time water in the electrolyte solution evaporates from the batterycausing the electrolyte solution level (the “electrolyte level”) tofall. If the electrolyte level falls below a minimal acceptable level ina battery, serious problems can occur to the battery such as reducedelectrical power output and/or permanent damage. For example, if theelectrolyte level drops below the top edge of a negative plate in thecell of a battery, the negative plate is exposed to air, which rapidlycauses the negative plate to oxidize.

To address this problem, numerous devices have been proposed formonitoring the electrolyte level in the battery to ensure that the wateris replenished before the electrolyte level drops below the minimalacceptable level. For instance, devices mounted outside the cell of abattery that indicate when the electrolyte level is low are now incommon use, see e.g., U.S. Pat. No. 5,936,382, entitled BatteryElectrolyte Level Monitor, issued Aug. 10, 1999, incorporated herein byreference. The common principle for most of these devices is a metalprobe inserted through the cover of a pilot cell in the battery.Typically, when the tip of the probe touches the electrolyte, the probesends a signal (via electrical circuitry) to an indicator, such as analarm or a light, indicating that the electrolyte level in the batteryis satisfactory. On the other hand, when the electrolyte level dropsbelow the tip of the probe, it sends another signal to the indicatorthat the time for re-watering the battery is imminent.

One drawback with these probe-based devices is they cannot easily readthe electrolyte level below the top edges of battery separators.Separators are porous plastic sheets that keep the plates apartelectronically, but permit ionic current flow between them. If the metaltip of the probe should touch the wet separator in general, or have anyionic contact with the separator whatsoever, for example through adroplet of electrolyte, or tarry substance, or wet particulate matter,etc., then this may cause the probe to continue sending a signalindicating that the electrolyte level is satisfactory, even though theelectrolyte may have fallen below the acceptable level. In other words,the probe causes the indicator to illicit a false indication that theelectrolyte level is satisfactory, when in fact, it is too low.

As a result, most battery manufacturers have kept their probe tips abovethe separators and require watering more frequently than is actuallyneeded. However, now there is a demand for batteries that are designedfor very low maintenance, i.e., very long watering intervals. That is,there is a desire to allow the electrolyte levels to drop to a levelthat is well below the level of the separators, such as to the tops ofthe plates.

To make the probes more accurate at measuring the electrolyte levelsbelow the separators without touching them, a mechanical “spreader” orshield is used to wedge the separators apart so that the probe candescend between them without touching them or having any ionic trackingpaths to the separators.

One limitation with this mechanical solution is the tight tolerancesinvolved. For example, the separators even in a large battery cell maybe only a few millimeters apart, and much less on smaller cells.Therefore, the risk of ionic contact with the separators is quite high,which results in a false signal.

Still another limitation with spreader designs is that a hole must beprovided in the cell's cover which is aligned perfectly above thepositive plate; otherwise, the probe will not fit precisely and maydamage the separators. Existing punch-out holes in many batter cellcovers, used routinely for level probes—generally do not line up withthe plates and cannot be used in conjunction with the spreader designs.The result is a second set of holes must be drilled into the cellcovers, which adds labor cost and inconvenience. Thus, there iscurrently no inexpensive and accurate way to measure electrolyte levelsin batteries once the electrolyte levels fall below the top of theseparators.

Another drawback associated with current probe designs is their failureto recognize when the electrolyte level in a battery cell falls belowthe level of the probe. Many times an indirect current path can stillexist from the tip of the probe, along the length of the probe, aroundthe inside of a battery cell and finally down the cell wall to thelowered electrolyte level. Although this path is of a higher resistancethan a direct current path from the probe tip submerged in theelectrolyte, the indirect current path may still cause a falseindication.

SUMMARY

A system and method for monitoring electrolyte levels in a battery isdescribed. According to one implementation, the system comprises ameasuring device and a controller. The measuring device is located in abattery and is configured to detect when the electrolyte level in thebattery falls below a particular level. The controller is in electricalcommunication with the measuring device. The controller is configuredto: (i) receive a signal from the measuring device indicating when theelectrolyte level in the battery has fallen below the particular level;(ii) introduce a wait-period after the signal is received; and (iii)enable an indicator to indicate that the electrolyte level in thebattery should be refilled after the wait-period expires.

The following description, therefore, introduces the broad concept ofusing a measuring device, such as a probe-based system, in conjunctionwith a programmable controller for monitoring the electrolyte level in abattery. The controller is configured to introduce a wait-period afterreceiving a signal from a measuring device indicating that theelectrolyte level in a battery cell has fallen below a particular level,e.g., a level above one or more separators in the battery cell. Thewait-period is intended to coincide with an approximate time it takesthe electrolyte level to fall from the particular level above theseparators to a level below the separators but above the top of platesin the battery cell. The controller introduces the wait-period withouthaving to physically measure the electrolyte level, after theelectrolyte level drops below the top of the separators in the batterycell. Accordingly, the controller waits for the wait-period to expirebefore enabling an indicator (e.g., an alarm, a light, a message, etc.)to indicate that the battery should be refilled.

The controller also eliminates the need to physically insert a measuringdevice below the separators where there is a high likelihood of touchingthe separators or making ionic contact with them. That is, the novelsystems and methods described herein are able to provide an indicationof the electrolyte level below the separators without a risk of touchingthe separators or making ionic contact with them. As such, a probe canbe inserted in standard punch-out holes provided in the casing of thebattery. No drilling or lining-up of the probe with the plates isrequired, reducing labor costs and inconveniences associated withpainstakingly attempting to insert the probe between the separators asmay be the case with conventional solutions as described above in theBackground.

According to another implementation, the electrolyte level in a batteryis monitored when fluid is being added to the battery, i.e., the batteryis being refilled. When the electrolyte level rises to a particularlevel a refill-wait-period is introduced. If the electrolyte level isdetected to remain at the particular level for the duration of therefill-wait-period, then an indicator is enabled indicating that theelectrolyte level in the battery has reached at least a desired level.The refill-wait-period is programmable duration that may be used toaccount for accidental splashing of fluids on a measuring device thatperforms level detection of the electrolyte when refilling the batterywith fluid.

According to still another implementation, the electrolyte level ismonitored in a battery to detect when the electrolyte level falls belowa particular level. A first wait-period is introduced when theelectrolyte level in the battery is detected to have fallen below theparticular level. The electrolyte level is then monitored to detectwhether it rises back above the particular level during the firstwait-period. If the electrolyte level in the battery does rise above theparticular level during the first wait-period, then the firstwait-period is reset. However, if the electrolyte level in the batterydoes not rise above the particular level during the first wait-period,then a second wait-period is introduced after the first wait-periodexpires. When the second-wait period expires, an indicator is enabledindicating that the electrolyte level in the battery should be refilled.

The first wait-period may account for situations when the battery probetemporarily emerges from the electrolyte, such as when the battery is inmotion or tilted on an angle. To ensure that this does not cause a falseindication that the battery needs to refilled, the first wait-period iscontinually reset each time the probe reenters the electrolyte. Onlyafter the first wait-period expires before being reset, i.e., when theprobe remains emerged from the electrolyte for the duration of thefirst-wait period, is the second-wait period initiated.

According to yet another implementation, a power management system isused to control power supplied to a probe. The system selectivelyenergizes and de-energizes the probe over time. When the probe isenergized, a high current is supplied to the probe to reduce theprobability of a false connectivity indication that the probe issubmerged in electrolyte, when in fact the electrolyte is below theprobe. Periodically, switching between the energized and non-energizedstates enables the overall average current draw to remain relatively lowover time despite supplying a high current to the probe. The relativelyhigh current enables the current draw between direct and indirect pathsto be large and easily distinguishable, increasing the accuracy ofelectrolyte level detection without incurring a penalty for using ahigher current.

This and other implementations will be described below when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears.

FIG. 1 illustrates a cross-sectional view of an exemplary aqueousbattery in which it is desirous to monitor electrolyte levels therein.

FIG. 2 illustrates a schematic diagram of an exemplary implementation ofa controller shown in FIG. 1.

FIG. 3 illustrates an alternative schematic diagram of another exemplaryimplementation of the controller shown in FIG. 1.

FIG. 4 illustrates an exemplary method for monitoring electrolyte levelsin a battery.

FIG. 5 illustrates a more detailed exemplary method for monitoringelectrolyte levels in a battery.

DETAILED DESCRIPTION

Exemplary Battery

FIG. 1 illustrates a cross-sectional view of an exemplary aqueousbattery 102, such as a lead acid or nickel-cadmium battery, in which itis desirous to monitor electrolyte levels therein. Battery 102 includes:a container 104, a negative plate 106(1), a positive plate 106(2), aseparator 108, and a vent 112. It is to be appreciated that additionalcomponents (not shown) can be included in battery 102. For example,additional plates, separators, vents, and so forth may be included inbattery 102. Additionally, battery 102 may comprise additional cellsthat are not necessarily located in the same container 104. It isassumed that those skilled in the art are familiar with the basiccomponents as well as the operational principles of an aqueous battery.

During charging of battery 102, water is electrolyzed to hydrogen andoxygen gases which exit container 104 via vent 112. The result is agradual lowering of the electrolyte level in battery 102.

Exemplary Monitoring System

Accordingly, connected to battery 102 is a novel monitoring system 126for monitoring the electrolyte level in battery 102. In the exemplaryimplementation, monitoring system 126 comprises a measuring device 128,an indicator 130, and a controller 132.

In one implementation, monitoring system 126 monitors three levels ofelectrolyte (electrolyte levels) in battery 102: a lowest electrolytelevel 114, an interim level 120, and a highest level 124. The lowestelectrolyte level 114 is the lowest safe level for electrolyte solutionshould be allowed to reach, which coincides to the tops 118(1) and118(2) of the plates 106(1) and 106(2). Interim level 120 coincides withthe top 122 of separator 108 and highest level 124 represents a maximumelectrolyte height recommended by the manufacturer of the battery and isusually the level after the battery 102 has been refilled with water orsome other type of solution. Other levels may also be monitored by themonitoring system 128.

Measuring device 128 may be any type of device configured to detect whenthe electrolyte level in the battery falls below a particular level. Forexample, in one implementation measuring device 128 comprises a probe134 inserted through a hole (not shown) in the top 136 of container 104.Probe 134 senses whether its tip 138 is submerged in the electrolyte orthe electrolyte level is below the tip 138 of probe 134. In other words,probe 134 is configured to detect whether the electrolyte level is aboveor below the particular level coinciding with tip 138, which in oneimplementation also coincides with the interim level 120. It is alsopossible that the particular level may coincide with other levels in thebattery, higher than the interim level or potentially lower than the top122 of separator 108.

In alternative implementations, probe 134 may be inserted from the side137 of container 104 instead of the top 136. Additionally, it is alsopossible to have multiple probes located in battery 102 (whether fromthe side or top), for measuring the electrolyte levels in differentcells and/or different electrolyte levels. It should be appreciated tothose skilled in the art that the measuring device 128 may take variousother forms, such as a strip, an optical sensor, or some other type ofmeasuring device capable of sensing whether the electrolyte level fallsbelow a particular level.

Indicator 130 is a device capable of providing an indication to peoplethat the battery may need to be serviced. For instance, in oneimplementation, indicator 130 is a light that remains illuminated whenthe electrolyte level is satisfactory, and is turned-OFF, i.e.,extinguished or deactivated, signaling that the time for refilling thebattery is imminent. Alternatively, the light may be illuminated when itis time for refilling and deactivated when the electrolyte level issatisfactory.

In other implementations, it is also possible for the indicator to beconfigured to provide different types of indications as the electrolytelevel approaches the lowest recommended electrolyte level 114. Forexample, the indicator 130 may provide a forewarning indication of adifferent color, such as yellow, indicating that the electrolyte levelis quickly approaching the lowest recommended electrolyte level 114. Ared light may then be illuminated when the electrolyte level actuallyreaches the lowest safe level, which coincides to the tops 118(1) and118(2) of the plates 106(1) and 106(2).

In alternative implementations, indicator 130 may take various formsincluding: an audio alarm, a message displayed on a display device suchas a user-interface on a dashboard, a message indicating whether theelectrolyte level is satisfactory or not such as an e-mail message sentover a network, multiple lights having various potential colors, ananalog or digital gauge showing a full and recommended refilling levels,a combination of any of the aforementioned formats, and other potentialindicators.

Controller 132 is a control module that controls the operation ofmonitoring system 126, such as when to enable indicator 130 to signal(i.e., indicate) that the electrolyte level in the battery should berefilled. In one implementation, controller 132 is connected tomeasuring device 128 and indicator 130 via a link 131, such as a wiredor wireless link. Accordingly, controller 132 is in “electricalcommunication” with measuring device 128 and indicator 130.

In one implementation, controller 132 includes one or more processor(s)150 that can be configured to implement the inventive techniquesdescribed herein. Processor(s) 150 process various instructions tocontrol the operation of the monitoring system 126 and possibly tocommunicate with other electronic and computing devices.

Controller 132 may also include one or more memory components 152 suchas volatile or non-volatile memory (also collectively referred to ascomputer readable media). For example, controller 132 may include afirmware component 154 that is implemented as a permanent memory modulestored in memory components 152. Firmware 154 is programmed and testedlike software, and may be distributed with battery 102 (or separately ona disk or over the Internet such as in the form of an update). Firmware154 can be implemented to coordinate operations monitoring system 126such as controlling the indicator 130, and contains programmingconstructs used to perform such operations.

Thus, memory components 152 may store various information and/or datasuch as configuration information, operating parameters about thebattery, charging information, and other information. For example,contained within memory components 152 are modules that contain code,such as in the form of firmware 154 and/or logic, used by controller 132to monitor whether the electrolyte level is above or below a particularlevel.

It is to be appreciated that the components and processes described withreference to controller 132 can be implemented in software, firmware,hardware, or combinations thereof. By way of example, a programmablelogic device (PLD) or application specific integrated circuit (ASIC)could be configured or designed to implement various components and/orprocesses discussed herein.

Controller 132 may include an input 137, which is one or more variety ofcomponents such as pin(s) on a microprocessor chip configured to receiveone or more signals from measuring device 128. The signals indicatewhether the electrolyte level in the battery is above or below aparticular level, such as interim level 120. The signals themselves maybe logical signals such as logical “one” indicating that the electrolytelevel has dropped below the particular level and logical “zero”indicating that the electrolyte level is above a particular level, orvice versa.

Controller 132 may also include an output 139 configured to transmit asignal to indicator 130 to induce indicator 130 to provide an indication(visual and/or auditory) whether the electrolyte level in the battery102 should be refilled or not and potentially other indications. Likeinput 137, output 139 represents one or more variety of components suchas pin(s) on a microprocessor chip configured to transmit one or moresignals.

Having introduced the various components of a exemplary battery andmonitoring system 126, it is now possible to describe specificfunctionality provided by monitoring system 126.

Wait Period

Controller 132 receives a signal (either active high or active low) frommeasuring device 128 indicating when the electrolyte level in battery102 has fallen below the interim level 120. At this point after thesignal is received, controller 132 introduces a wait-period. Thewait-period is intended to coincide with an approximate time it takesthe electrolyte level to fall from the particular level above theseparators to a level below the separators but above the tops 118(1) and118(2) of the plates 106(1) and 106(2). Controller 132 introduces thewait-period without having to physically measure the electrolyte level,after the electrolyte level drops below the top 122 of separator 108.Accordingly, controller 132 waits for the wait-period to expire beforeenabling indicator 130 (e.g., an alarm, a light, a message, etc.) toindicate that the time for refilling the battery should be performed.

Controller 132 when used in conjunction with a measuring deviceeliminates the need to physically insert measuring devices below aseparator 108 where there is a high likelihood of touching the separator108 or making ionic contact with it. That is, monitoring system 126provides an indication of the electrolyte level below a separatorwithout risking touching the separators or making ionic contact withthem. As such, a probe can be inserted in standard punch-out holesprovided in the container 104 of battery 102. No drilling or lining-upof a measuring device 128 (such as a probe) with plates 106 is required,reducing labor costs and inconveniences associated with painstakinglyattempting to insert the probe between the separators as may be the casewith conventional solutions as described above in the Background.

Using a programmable controller 132 also facilitates providing anextremely low maintenance battery, i.e., a battery with very longwatering intervals. The extra increment of time gained between wateroperations attained by introducing the wait-period in accordance withthe novel implementations described herein, reduces the water intervalsand adds commercial value to the battery. By allowing the electrolytelevel to drop to the top of the plates 106, well below the tops of oneor more separators, extends the water maintenance interval time overthat of most batteries with conventional probe-based detection systems.In essence the battery is considered to be a lower maintenance battery.

In one implementation, controller 132 includes a wait-module 156configured to introduce the wait-period after the signal is receivedfrom the measuring device 128 indicating that the electrolyte level inthe battery has fallen below a particular level, such as the interimlevel 120.

In one implementation, the wait-period is a programmable period of timethat may be predetermined and programmed into controller 132. Thewait-period may include any period of time, but typically ranges fromhours-to several days. For example, for most batteries it is anticipatedthat the wait-period will range from one or more days to about 50 daysor more, before controller 132 enables indicator 130 to indicate thatthe time for refilling battery 102 has arrived.

Wait-module 156 may determine the wait-period several different ways.For instance, in one implementation, the wait-period is a programmableperiod of time. Controller 132 may comprise a counter 158 configured tocountdown the programmable period of time to determine the wait-period.

According to another implementation, controller 132 may comprise acharging-cycle module 160, which is configured to monitor how manycycles of charging the battery experiences as a function of determiningthe wait-period, i.e., the period of time used by counter 158 tocountdown. According to this implementation, controller 132 would beconfigured keep track of charging cycles.

According to another implementation, controller 132 may comprise awater-loss estimation module 162, configured to estimate a rate ofelectrolyte loss for the battery as a function of the age of thebattery, and adjust the wait-period (i.e., the period of time used bycounter 158 to countdown) accordingly. For example, water-lossestimation module 162 may take into account variable water consumptionrates of old versus new batteries containing antimonial grids.

According to yet another implementation, controller 132 may comprise atemperature/charge-rate compensation module 164 to further estimate await-period.

Thus, the wait-period may be preset or be dynamically adjusted toaccount for various parameters, such as the age of the battery,temperatures, charging cycles, water-rate-loss, etc.

First and Second Wait Periods

According to still another implementation, controller 132 monitors theelectrolyte level battery 102 to detect when the electrolyte level fallsbelow a particular level, such as interim level 120. This time anotherwait-period is introduced called, a “first wait-period” when theelectrolyte level in the battery is detected to have fallen below theparticular level. The electrolyte level is then monitored to detectwhether it rises back above the particular level during the firstwait-period. If the electrolyte level in the battery does rise above theparticular level during the first wait-period, then the firstwait-period is reset (a counter is reset). However, if the electrolytelevel in the battery does not rise above the particular level during thefirst wait-period, then a second wait-period (typically a longer“wait-period” such as described above) is introduced after the firstwait-period expires. When the second-wait period expires, controller 132enables indicator 130 to indicate that the electrolyte level in thebattery should be refilled.

The first wait-period is designed to account for situations whenmeasuring device 128 temporarily emerges from the electrolyte, such aswhen the battery is in motion or tilted on an angle. To ensure that thisdoes not cause a false indication that the battery needs to refilled,the first wait-period is continually reset each time the probe reentersthe electrolyte. Only after the first wait-period expires before beingreset, i.e., when the measuring device 128 remains emerged from theelectrolyte for the duration of the first-wait period, does thecontroller 132 initiate the second-wait period.

In one implementation, the first wait-period is a programmable period oftime that may be predetermined and programmed into controller 132. Thefirst wait-period may include any period of time, but typically rangesfor only a few seconds to several minutes. For example, the first waitperiod may be set to start after about three seconds, and if themeasuring device 128 does not remain the electrolyte for about 30continuous seconds, then the second wait-period will be initiated.

Wait-module 156 may determine the “first wait-period” several differentways. For instance, in one implementation controller 132 may comprise acounter 166 configured to countdown the programmable period set for thefirst wait-period. For instance, counter 166 counts may be set to startafter about three seconds (another counter, not shown, may be used tostart the initial count period) and if the measuring device 128 does notremain the electrolyte for about 30 continuous seconds, then the secondwait-period will be initiated. Otherwise, counter 166 will be reset ifthe measuring device 128 is re-immersed in electrolyte before reachingthe end of the 30 second countdown period (i.e., the first wait-period).

Refill Wait-Period

According to another implementation, monitoring system 126 also monitorsthe electrolyte level in battery 102 when fluid is being added tobattery 102. When the electrolyte level rises to a particular level,controller 132 introduces a refill-wait-period. If the electrolyte levelis detected to remain at the particular level for the duration of therefill-wait-period, then controller 132 enables indicator 130 toindicate that the electrolyte level in the battery 102 has reached atleast a desired level.

The refill-wait-period is programmable for a duration that may be usedto account for accidental splashing of fluids on measuring device 128when refilling the battery with fluid. For instance, a mere splash ofacid onto a probe could reset the logic in controller 132 and enable theindicator 130 to indicate that the battery 102 is full. This may cause amaintenance operator servicing the battery to think that the cell(s) ofthe battery are full when they are not, which may cause confusion.Accordingly, an appropriate time delay (the refill-wait-period)configured in controller 132, ensures that the indicator does notindicate that cell(s) of battery 102 are full until measuring device 128makes continuous contact with the electrolyte for the period of the timedelay.

For instance, in one implementation controller 132 may also include arefill module 170 configured to introduce the refill-wait-period. In oneimplementation, the refill wait-period may be set for several seconds,i.e., such as two to ten seconds or enough to account for accidentalsplashing. A counter 172 may countdown the re-fill period to ensure thatthe electrolyte level makes continuous contact with the measuring device128 before enabling controller 132 to enable indicator 130.

Power Management

According to yet another implementation, controller 132 may comprise apower management module 176 to control power supplied to the measuringdevice 128. That is, controller 132 selectively energizes andde-energizes the measuring device 128 over time. When the measuringdevice 128 is energized, a high current is supplied to the measuringdevice to reduce the probability of a false connectivity indication thatthe measuring device 128 is submerged in electrolyte, when in fact theelectrolyte is below the electrolyte detection device. Periodically,switching between the energized and non-energized states enables theoverall average current draw (or voltage draw) to remain relatively lowover time despite supplying a high current (or voltage) to the measuringdevice device. Whereas, the relatively high current enables the currentdraw between direct and indirect paths to be large and easilydistinguishable, therefore increasing the accuracy of electrolyte leveldetection without incurring a higher current draw.

In one implementation, the high current supplied to the measuring deviceis about approximately 100 milliamperes, however, the high current couldalso be greater or smaller. For instance, the high current could be lessthan 100 milliamperes, so long as the high current is distinguishablefrom the indirect current paths.

In one implementation, controller 132 selects (i.e., switches) between atest mode and a non-test mode. During the test mode, controller 132energizes measuring device 128 to enable the measuring device 128 toascertain whether the electrolyte level is above or below a particularlevel. During the non-test mode controller 132 deactivates (orde-energizes power to) measuring device 128. In one implementation,controller switches between the test mode and non-test mode about everysecond. However, during the period of the test mode controller 132 onlyrequires a few milliseconds to determine the status of the measuringdevice 128, i.e., whether the electrolyte level is above or below themeasuring device 128. Thus, energizing the measuring device 128 for onlya few milliseconds before de-energizing it, allows current draw overtime to remain on average at about five milliamperes, or equivalent toconstantly energizing the measuring device 128 with a smaller current.

Although controller 132 is shown to include various distinct functionalblocks (a wait module 156, a water-loss estimation module 162, a refillmodule 170, etc.), it is understood that when actually implemented inthe form of computer-executable instructions, logic, firmware, and/orhardware, that the functionality described with reference to each blockmay not exist as separate identifiable modules. Controller 132 may alsobe integrated with other components or as a module in a larger system.

Exemplary Implementations of Control Module

FIG. 2 illustrates a schematic diagram of an exemplary implementation ofthe controller 132 shown in FIG. 1. Referring to FIG. 2, an input 231 ofthe controller 132 is coupled to a measuring device 126 (FIG. 1). Input231 is coupled to the base 232 of transistor 233 across resistor 235 andis also coupled across resistor 237 to terminal 239, which is coupled to−VE potential of battery 102.

Resistor 237 serves as a current to voltage translator, creating avoltage drop across resistor 237 when current flows from input 231 toterminal 239. Resistor 235 serves to limit the amount of current thatflows to base 232 of transistor 233.

When measuring device 128 (FIG. 1) is immersed in the electrolytecontained in container 104 (FIG. 1), the electrolyte functions to closethe circuit between first input 231 and terminal 239. This creates avoltage drop across resistor 235 sufficient to drive transistor 233 intosaturation. When transistor 233 is on, the circuit path from terminal238 to terminal 239 is closed through resistor 244. This results incausing a low level logic or logical zero being applied to pin 4 of amicrocontroller 240.

When measuring device 126 is not immersed in the electrolyte, thecircuit between input 231 and terminal 239 is opened. This causes thepotential between the base 232 of transistor 233 and the drain ofterminal of transistor 233 to become zero and transistor 233 turns off.This will cause pin 4 of microcontroller 240 to realize an input voltageequal to terminal 238 i.e., +VE. This is equivalent of a logical oneprovided to pin 4.

Microcontroller 240 is programmed to recognize the change from a logicalzero to a logical one on pin 4 as an indication that the measuringdevice 126 is no longer immersed in the electrolyte in battery 102, andcontrol indicator 130 (which in this implementation comprises two LEDs),which is coupled to microcontroller 240 after one or more wait-periodsaccording to preprogrammed set of conditions.

In the exemplary implementation illustrated in FIG. 2, microcontroller240 is a 12F629 chip manufactured by Microchip of Chandler, Ariz., USA.It is, however, understood that one of skill in the art would appreciatethat numerous chips and/or other devices could be used in place of thisspecific microcontroller 240.

A clock circuit 245 comprising a crystal controlled clock 246 and a setof capacitors 247 and 248 facilitate control of indicator 130 bymicrocontroller 240. Clock circuit 245 provides the time mechanismrequired to allow microcontroller 240 to control indicator 130 inaccordance with preprogrammed conditions.

FIG. 3 illustrates an alternative schematic diagram of another exemplaryimplementation of controller 132 shown in FIG. 1. FIG. 3 includes theaddition of a switch 302 coupled to both the microcontroller 240 andmeasuring device 128. Microcontroller 240 operates in a selectable testmode and non-test mode. When microcontroller 240 selects the test mode,microcontroller 240 enables power to be supplied to measuring device128. That is, the microcontroller 240 causes the switch 302 to couplethe power supply +VE/−VE to measuring device 128 when themicrocontroller is in the test mode, which energizes the measuringdevice and allows microcontroller 240 to determine whether theelectrolyte level in the battery is above or below a particular level.When in the non-test mode, microcontroller 240 disconnects (decouples)measuring device 128 enabling the measuring device 128 to bede-energized. Repetitively switching between the test mode and thenon-test mode causes the measuring device to be energized andde-energized repetitively over time, which allows a high current to besupplied to the measuring device 128, when in the test mode.

Methods of Operation

FIG. 4 illustrates an exemplary method 400 for monitoring electrolytelevels in a battery. Method 400 enables the electrolyte levels to bemonitored below the tops of separators in a battery without having toactually insert a sensor below the separators. Method 400 includesblocks 402, 404, 406 and 408 (each of the blocks represents one or moreoperational acts). The order in which the method is described is not tobe construed as a limitation, and any number of the described methodblocks can be combined in any order to implement the method.Furthermore, the method can be implemented in any suitable hardware,software, firmware, or combination thereof.

In a decisional block 402, the electrolyte level in the battery ismonitored to detect whether it falls below a particular level. Forexample, controller 132 (FIG. 1) detects whether tip 138 (FIG. 1) ofprobe 134 (FIG. 1) is submerged in the electrolyte or the electrolytelevel is below the tip 138 (FIG. 1), which generally coincides with alevel the top 122 (FIG. 1) of separator 108 (FIG. 1) in battery 102(FIG. 1). If the electrolyte level is not below the particular level,then according to the NO branch of decisional block 402, method 400loops back and continues to monitor the electrolyte level. If theelectrolyte level falls below the particular level, then according tothe YES branch of decisional block 402 method 400 proceeds to block 404.

In block 404, if the electrolyte falls below the particular level asignal is received by the controller 132 (FIG. 1) indicating thatelectrolyte level is below the particular level.

In block 406, a wait-period is introduced when the electrolyte level inthe battery 102 is detected to have fallen below a particular level. Forexample, controller 132 starts a counter 158 that counts down aparticular period of time.

In block 408, a warning is made that the electrolyte level in thebattery should be refilled after the wait-period expires. For example,controller 132 sends a signal to indicator 130 enabling it to indicate(light, sound an alarm, display a message, etc.) that water should beadded to battery 102.

FIG. 5 illustrates a more detailed exemplary method for monitoringelectrolyte levels in a battery. Method 500 includes blocks 551, 553,555, 557, 559, 561, 563 and 565 (each of the blocks represents one ormore operational acts). The order in which the method is described isnot to be construed as a limitation, and any number of the describedmethod blocks can be combined in any order to implement the method.Furthermore, the method can be implemented in any suitable hardware,software, firmware, or combination thereof.

In block 551 an indicator is turned-OFF (in this example when theindicator is turned-OFF it is actually enabled—meaning that theelectrolyte level needs to be refilled). In a decisional block 553 adetermination is made whether a measuring device has been in theelectrolyte for a short period time, such as several seconds. Ifaccording to the YES branch of decisional block 553, the measuringdevice has been immersed in the electrolyte for the short period of time(e.g., three seconds), method 500 proceeds to block 555. If according tothe NO branch of decisional block 553, the measuring device has not beenimmersed in the electrolyte for the short period of time, then method500 proceeds back to block 551.

In block 555 an indicator is enabled. For example, a light (e.g., lightemitting diode) is turned-ON, meaning the indicator is actuallyindicating that the electrolyte level is satisfactory and does not needto be refilled.

In a decisional block 557, a determination is made whether the measuringdevice remains immersed in the electrolyte for another short duration oftime. For example, a determination is made whether the measuring device128 (FIG. 1) remains in the electrolyte for thirty continuous seconds.If according to the NO branch of decisional block 557, if the measuringdevice does not remain in the electrolyte, method 500 proceeds to block553. If according to the YES branch of decisional block 557, if themeasuring device does remain the electrolyte, method 500 proceeds toblock 559.

In block 559 a timer for a clock is initiated, i.e., a counter startscounting down the wait-period. However, according to the YES branch ofdecisional block 561, if the measuring device remains in the electrolytethe counter will either be reset or will not count-down, and method 500returns to block 559.

If according to the NO branch of decisional block 561, if the measuringdevice does not remain in the electrolyte, method 500 proceeds to block563 and the counter counts down the wait-period, (whether predeterminedor dynamically chosen depending on various parameters such as age of thebattery, charging cycles, water loss rate, etc.).

Once the wait-period expires, e.g., counter finishes counting down thewait-period, method 500 proceeds to block 551 and turns-off indicator130 (e.g., enables indicator to indicate that aqueous solution should beadded to battery 102 because the electrolyte level has most likelyreached the tops of the battery plates.

Although the invention has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the invention defined in the appended claims is not necessarilylimited to the specific features or acts described. Rather, the specificfeatures and acts are disclosed as exemplary forms of implementing theclaimed invention.

1. A system for monitoring the electrolyte level in a battery having oneor more separators between positive and negative plates in a cell of thebattery, the one or more separators having a top which is at a levelthat is higher than a top of the plates, said system comprising: ameasuring device, suitable to be located in said battery, configured todetect when the electrolyte level in the battery falls below a firstlevel which is above the tops of the separators in said battery; and acontroller, in electrical communication with the measuring device,configured to (i) receive a signal from the measuring device indicatingwhen the electrolyte level in the battery has fallen below said firstlevel, (ii) introduce a wait-period after the signal is received, and(iii) enable an indicator to indicate that the electrolyte in thebattery should be refilled after the wait-period expires; wherein saidwait-period represents an appropriate time it takes the electrolytelevel to fall from said first level to a second level which is below thetops of said separators and above the tops of said plates.
 2. The systemas recited in claim 1, wherein during the wait-period the controller isfurther configured to enable the indicator to indicate that theelectrolyte level in the battery is approaching said second level as aforewarning to actually providing the indication that the electrolytelevel in the battery should be refilled.
 3. The system as recited inclaim 1, wherein the wait-period is a programmable period of time. 4.The system as recited in claim 1, wherein the controller comprises acounter configured to count down a programmable period of timecomprising the wait-period.
 5. The system as recited in claim 1, whereinthe controller comprises a charging-cycle module configured to monitorthe number of cycles of charging the battery experiences after saidsignal is received and wherein said wait-period is a function of saidnumber of cycles of charging.
 6. The system as recited in claim 1,wherein the controller comprises a water-loss estimation module,configured to estimate a rate of electrolyte loss for the battery as afunction of the age of the battery, and adjust the wait-periodaccordingly.
 7. The system as recited in claim 1, wherein the indicatoris one or more lights that are activated to signify that the electrolytelevel in the battery should be refilled.
 8. A battery, comprising: oneor more cells having disposed therein positive and negative plates, aseparator disposed between said positive and negative plates, and aliquid electrolyte within said cells having an electrolyte level, saidseparator having a top which is at a level above a top of said positiveand negative plates; a probe, located in at least one of said batterycells, configured to detect when said electrolyte level falls below afirst level which is above the tops of said separators; an indicator;and a controller, in electrical communication with the probe, configuredto (i) receive a signal from the probe indicating when the electrolytelevel in the battery has fallen below said first level, (ii) introduce await-period after the signal is received, and (iii) enable the indicatorto signify that the electrolyte in the battery should be refilled whenthe wait-period expires; wherein said wait-period is chosen to allow theelectrolyte level to fall from said first level to a second level whichis below the tops of said separators and above the tops of said positiveand negative plates.
 9. The battery as recited in claim 8, furthercomprising an electrical circuit connecting the controller to the probe,the electrical circuit configured to enable the signal to be sent to thecontroller when the probe detects that the electrolyte level is belowsaid first level.
 10. The system as recited in claim 1, furthercomprising: means for receiving the signal from the measuring deviceindicating whether the electrolyte level in the battery is above orbelow the measuring device; and means for repetitively energizing andde-energizing the measuring device over time.
 11. The system as recitedin claim 10, wherein the means for repetitively energizing andde-energizing the measuring device over time comprises the controller.12. The system as recited in claim 10, wherein the means for receivingthe signal from the measuring device is an input terminal of thecontroller.
 13. The battery as recited in claim 8, further comprising:means for receiving the signal from the probe indicating whether theelectrolyte level in the battery is above or below the probe; and meansfor repetitively energizing and de-energizing the probe over time. 14.The battery as recited in claim 13, wherein the means for repetitivelyenergizing and de-energizing the probe over time comprises thecontroller.
 15. The battery as recited in claim 13, wherein the meansfor receiving the signal from the probe is an input terminal of thecontroller.
 16. A system for monitoring the electrolyte level in abattery having one or more separators between positive and negativeplates in a cell of the battery, the separator having a to that is at alevel which is higher than a to of the plates, said system, comprising:a measuring device for detecting when an electrolyte level in thebattery falls below a first level which is above said top of said one ormore separators, said measuring device comprising a probe positioned atsaid first level; and a controller, in electrical communication with themeasuring device, configured to (i) receive a signal from the measuringdevice indicating when the electrolyte level in the battery has fallenbelow said first level, (ii) introduce a wait-period after the signal isreceived, the wait-period being chosen to allow the electrolyte level tocontinue to fall to a second level which is below the tops of saidseparators and above the tops of said plates, and (iii) enable anindicator to indicate that the electrolyte in the battery should berefilled after the wait-period expires.
 17. A system for monitoring theelectrolyte level in a battery having a separator between positive andnegative plates in a cell of the battery and a lowest recommendedelectrolyte level which is above the positive and negative plates, theseparator having a top which is at a level that is higher than thelowest recommended electrolyte level, said system comprising: ameasuring device, located in said battery, configured to detect when theelectrolyte level in the battery falls below a first level which isabove the to of said separator; a controller, in electricalcommunication with the measuring device, configured to (i) receive asignal from the measuring device indicating when the electrolyte levelin the battery has fallen below the first level, (ii) introduce await-period after the signal is received, and (iii) enable an indicatorto indicate that the electrolyte in the battery should be refilled afterthe wait-period expires; and wherein said wait-period is chosen to allowthe electrolyte level to fall from said first level to a second levelwhich is below the top of said separator and no lower than said lowestrecommended electrolyte level.